【作者】 向文英；

【导师】 李晓红；

【作者基本信息】 重庆大学 ， 采矿工程， 2007， 博士

【摘要】 为满足海洋资源的开发与水下切割的需要,空化水射流与磨料射流得到不断的发展。同时,含砂水流通过各种水力机械(如水泵、水轮机等)、水工建筑时存在严重的空蚀现象有待研究,固、液、气多相流动的研究也很不完善。目前国内外对淹没环境下磨料射流中磨料与空泡的相互关系的研究还处于空白。本文从理论上系统地分析了淹没射流中磨料与空泡的相互关系,以及磨料射流的空蚀特性,实验研究了纯水空化射流和含有空泡的磨料射流的岩石破碎性能。得到以下重要结果:①通过对空泡的运动特性研究,建立了磨料射流的空泡运动方程。在单颗粒磨料受力分析基础上,建立了磨料群的运动方程。给出了空泡溃灭历时随磨料浓度、流场压力的变化,以及给出了磨料颗粒速度分布规律。②按微观运动理论,分析了含有空泡的磨料射流运动特性,建立了空泡、磨料、水体各相分别满足的动量方程。数值模拟和分析了淹没磨料射流的流场和压力场。得到:颗粒相速度比水相减少,颗粒相最大滞止压强较水相增加。研究了含有空泡的磨料射流的紊动特性、出流特性、和空化特性。指出,相同条件下含有空泡的磨料射流的空化数较纯水空化射流大,磨料射流的空化能力有所降低。纯水空化射流主要依靠空泡溃灭作用使靶体破坏,含有空泡的磨料射流则是磨料的磨损与空蚀两者共同作用使得靶体破坏。纯水空化射流的空泡溃灭压强略大于含有空泡的磨料射流。③在纯水空化射流与低浓度的磨料射流中,空泡云的发育过程经历了空泡云的膨胀、压缩、再膨胀、压缩、溃灭的几个过程。纯水空化射流产生的空泡云长度随泵压增加而增加;随着围压的增加,空泡云长度存在一最优围压。低浓度的磨料射流中,空泡云长度随着泵压增加先扬后抑;随着围压增加,空泡云长度出现不稳定性。④实验研究表明,在相同泵压时,文丘里型空化喷嘴产生的空化射流比普通收缩喷嘴具有更强的冲蚀能力,对砂岩的深度冲蚀能力平均是普通射流的2倍;质量冲蚀能力平均是普通射流的7倍;切缝直径是普通射流的2.3倍。对于含有空泡的磨料射流,围压增加空化噪音减少,泵压增加空化噪音增加;有效靶距直径比增加,对花岗岩的冲蚀深度与冲蚀质量存在一最优有效靶距直径比;在最佳冲蚀时间下,较纯水空化射流工作效率提高2倍。随泵压的增加,对花岗岩的冲蚀质量、冲蚀深度增加;随围压的增加,冲蚀质量、冲蚀深度减少,最优围压与纯水空化射流相同。本研究的主要创新之处在于:通过分析研究淹没状态下磨料射流中磨料与空泡的相互关系,建立了磨料射流的空泡运动方程和磨料群的运动方程;按微观运动理论建立了含有空泡的磨料射流的动量方程;给出了含有空泡的磨料射流的空化数变化规律,以及空泡溃灭压强的范围。这对含有空泡的磨料射流在深海深水中的应用奠定理论和实验基础。更多还原

【Abstract】 In order to satisfy the needs of exploiting ocean resources and incising under water , cavitation water jets and abrasive water jets have been developed. The cavitation of waterpower mechanism (such as pump and water motor) and water project construction through water current with sand need studying. The research of three multiphase of solid and liquid and gas has not been perfect. The research of the relationship between solid particles and bubble of abrasive water jets in the condition submerged by water has not been done at present all over the world.This paper will study systematically and theoretically the relationship of solid particles and bubble in submerged water jets, and the cavitation characteristic of abrasive water jets. Then it will experiment the capability of rock-erosion by cavitation water jets and by abrasive water jets with bubble. The important findings are as follows.①By analyzing bubble athletics characteristic, the bubble athletics equation in abrasive water jets was established. On the basis of the force analysis of single particle, athletics equation of the group abrasive particles has been set up. The study suggests that the time that a bubble collapses varies with the concentration of abrasive particles, and the fluid pressure, and shows the velocity distribution of the abrasive particles.②The momentum equations of liquid, bubble and solid particle have been set up after the athletic disciplinarian of abrasive water jets with bubble was analyzed from microcosmic movement theory. It were simulated for the velocity and the pressure of the submerged abrasive water jets. Show that the velocity of solid particles is smaller than water phase , and its dynamic pressure is bigger than water phase . The characteristics of the turbulent and the overflow, and the cavitation characteristic of abrasive water jets with bubble have been studied. Then it is pointed out that the cavitation number of abrasive water jets with bubble is bigger than that of cavitation water jets under the same condition, and the ability of cavitation of abrasive water jets decreases slightly. The cavitation water jets erodes the target by the bubble collapsing while the abrasive water jets with bubble incise and break the target by the erosion and abrasion. The bubble collapse pressure of cavitation water jets is bigger than that of abrasive water jets with bubble slightly.③The growth of bubble cloud experiences swelling and compressing, reinflating and recompressing, collapsing and falling in the cavitation water jets or abrasive water jets with bubble. The length of bubble cloud produced by cavitation water jets increases with pump pressure and as it does, it has a best ambient pressure. In the low–concentration abrasive water jets with bubble, the length of bubble cloud firstly increases and then decreases with the increase of pump pressure and it is unsteady as ambient pressure increases.④The experiment shows : With the same pump pressure, the capability of cavitation water jets produced by wenqiuli nozlle is stronger than common water jets. The average depth of erosion on gritstone for cavitation water jets is 2 times as much as common water jets, and its mass erosion is 7 times as much as common water jets, and its diameter of erosion is 2.3 times as much as common water jets.The erosion experimentation of abrasive water jets with bubble indicates: The noise of cavitation decreases with ambient pressure, while it increases with pump pressure. The depth and mass erosion on granitic decrease with the increasing of ratio of efficient standoff distance to diameter. At the best erosion time, the work efficiency is three times as much as cavitation water jets. The mass erosion and depth erosion on granitic increase with pump pressure, while they decrease with ambient pressure, and have a best ambient pressure which is the same as cavitation water jets.The main innovation of the dissertation is that: By analyzing the relationship between solid particles and bubble of abrasive water jets submerged by water, the bubble athletics equation in abrasive water jets and the group abrasive dynamic equation have been established . The momentum equations of abrasive water jets with bubble has been investigated based on microcosmic movement theory . The change domain of cavitation number and bubble collapse pressure have been gained . These provide the theoretical and experimental basis for the application of abrasive water jets with bubble in deep water and deep sea.更多还原